The present invention relates to a method of making one-piece lidded containers, and more particularly one-piece domed containers.
One-piece lidded containers (e.g., domed or clamshell containers) are commonly used in supermarkets and other food stores to package salads, muffins, prepared foods and the like. The containers are formed by thermoforming a length of thermoplastic material to provide a bottom tray having a container structure and top tray having a corresponding lid (e.g., dome) structure. The bottom and top trays are connected by a portion of the thermoplastic material that acts as a living hinge.
For a variety of commercial applications, it would be desirable to make a one-piece lidded container of dissimilar materials and dimensions. An example of such a combination would be a one-piece lidded container of oriented and non-oriented thermoplastic material. Another example would be one-piece lidded container formed from similar or dissimilar thermoplastic materials of differing thicknesses, barrier characteristics, heat sealabilities and other differing properties. Two-piece containers are often formed from thermoplastic materials having dissimilar properties.
For other commercial applications, multiple color schemes for these types of containers are desired. One particular color scheme often used is an opaque bottom with a clear top. However, the production of such multi-hued containers is generally not feasible with bioriented thermoplastic materials, since the technique for forming such containers is to thermoform a side-by-side coextruded sheet of opaque and clear thermoplastic material. Oriented materials (e.g., oriented polystyrene) are not used since a sharp delineation is not achievable between the opaque and clear portions of the coextruded sheet once the sheet is oriented in the transverse direction. Typically, cast sheets such as poly(ethylene terephthalate) (PET) would be used for such applications.
Another solution for incorporating oriented materials into multi-hued containers is to laminate a strip of opaque oriented material onto a sheet of clear oriented material. The two layered portion of the sheet, when thermoformed, provides the opaque container structure. While this technique provides a sharp delineation between the opaque and clear portions, the technique also has its disadvantages. For example, the usage of material is inefficient since a double layer of material is used to provide an opaque section. Likewise, the use of an adhesive reduces the recyclability of scrap and trim. These disadvantages, among others, increase production costs and time.
Thus, there is a need in for a method of making one-piece lidded containers from stock material that can be dissimilar in composition and dimensions. Likewise, there is a need in the art for a method of making one-piece lidded containers with multiple color schemes that enable a sharp delineation of colored materials while at the same time optimizing usage of materials. Accordingly, it is an object of the present invention to provide such methods and one-piece lidded containers made from such methods.
The present invention provides methods of making one-piece lidded containers that facilitate optimized usage of material. In a first embodiment, the method includes providing a first length of thermoplastic material and a second length of thermoplastic material and positioning a portion of the first and second lengths to provide an overlap juncture of thermoplastic material. The first and second lengths of thermoplastic material are secured to each other at the overlap juncture preferably by different methods of sealing (heat, ultrasound etc.) or adhesive attachment. At least a first container and at least a corresponding lid are formed on the first and second lengths of thermoplastic material, respectively. The container and corresponding lid structures are preferably formed by thermoforming. Thermoplastic material to be used are oriented thermoplastic materials, non-oriented thermoplastic materials, and combinations thereof. One preferred oriented thermoplastic material is oriented polystyrene. A preferred non-oriented thermoplastic material is polyethylene terephthalate or polystyrene. The first and second lengths of thermoplastic material can have different properties such as dissimilar thicknesses, different colors, differing barrier characteristics, among others. One preferred color combination is where first length of thermoplastic material is opaque and the second length of thermoplastic material is clear. In addition, the first and second lengths of thermoplastic material are preferably each of a single-layer of thermoplastic material. A preferred structure for the corresponding lid is a dome structure. The overlap juncture of thermoplastic material is preferably positioned between the container and corresponding lid. However, as described later in some instances the overlap juncture can be incorporated into the lid or the container itself.
The method can further include providing a hinge means between the first container and the corresponding lid. In one preferred embodiment a hinge means is provided by folding the thermoplastic material at a position between the container and the corresponding lid in a direction substantially the same as the overlap juncture. Optionally, the method can provide for further scoring of the overlap juncture to facilitate folding of thermoplastic material. Other hinge means can also be provided.
In another embodiment, present invention provides a method of making one-piece lidded containers, which includes providing a first, a second and a third length of thermoplastic material. A portion of the first and second lengths of thermoplastic material are positioned to provide a first overlap juncture of thermoplastic material. Likewise, a portion of the second and third lengths of thermoplastic material are positioned to provide a second overlap juncture of thermoplastic material opposite from the first juncture. The thermoplastic material of the first and second overlap junctures, respectively, are secured by different methods of sealing or in some instances with an adhesive or sealant. At least a first container and at least a second container are formed on the first and third lengths of thermoplastic material. Similarly, at least a first corresponding lid and at least a second corresponding lid are formed on the second length of thermoplastic material. Lastly, the second length of thermoplastic material is severed between the first and second corresponding lids to provide at least two sets of one-lidded containers. The first and second containers are preferably formed at a position other than the first and second overlap junctures. Likewise, the first corresponding lid and the second corresponding lid are preferably formed on the second length of thermoplastic at a position other than the first and second overlap junctures. The first corresponding lid is preferably positioned proximal to the first container while the seocnd corresponding lid is preferably positioned proximal to the second container. Hinge means can also be provided between the containers and lids of the one-piece lidded containers.
In an alternative embodiment, a method is provided for making at least one one-piece lidded container which includes providing a first length of thermoplastic material and a second length of thermoplastic material and forming at least a first container and at least a corresponding lid on the first and second lengths of thermoplastic material, respectively. A portion of the first and second lengths of thermoplastic material are positioned to provide an overlapping juncture of thermoplastic material after the container lid is formed that allows alignment of the container and corresponding lid to later close in a axially opposing orientation. Once positioned, the thermoplastic material at the overlap juncture is secured to form the one-piece lidded container.
In another alternative embodiment, a method is provided for making one-piece lidded containers which includes providing a first, a second and a third length of thermoplastic material. At least a first container and at least a second container are formed on the first and third lengths of thermoplastic material. Likewise, at least a first corresponding lid and at least a second corresponding lid are formed on the second length of thermoplastic material. A portion of the first and second lengths of thermoplastic material is positoned to provide a first overlap juncture of thermoplastic material that allows alignment of the first container and the first corresponding lid in an axially opposing orientation upon closure. A portion of the second and third lengths of thermoplastic material is also positioned to provide a second overlap juncture of thermoplasic material opposite from the first overlap juncture and allows alignment of the second container and the second corresponding lid in an axially opposing orientation upon closure. The thermoplastic material of the first and second overlap junctures, respectively, are secured by various sealing means. Lastly, the second length of thermoplastic material between the first and second corresponding lid is severed to provide at least two sets of one-piece lidded containers.
In yet another alternative embodiment, a method is provided for making a one-piece lidded container which includes juxtapositioning a first length of thermoplastic material with a second length of thermoplastic material to provide a juncture in the form of an abutment of thermoplastic material. The abutting lengths of thermoplastic materials can be secured directly by a sealant or an adhesive bead, or by a joining strip that is attached to both thermoplastic materials in the same direction as the abutment of material. At least a first container and at least a corresponding lid are formed on the first and second lengths of thermoplastic material, respectively. Preferably, the juncture of thermoplastic materials is positioned between the first container and the corresponding lid. The same method of attaching the first and second lengths of thermoplastic materials can be used to attach the three thermoplastic materials previously indicated.
A method is also provided for making one-piece lidded container which includes providing a bottom tray which is formed from a length of thermoplastic material, and providing a top corresponding lid which is formed from a second length of thermoplastic material. The bottom tray and top lid are aligned in an axially opposing orientation to form a closed container which provides a lapping juncture of thermoplastic material from a contiguous portion of the bottom tray and top lid. The bottom and top lid are secured to each other to form the one-piece lidded container.
One-piece lidded containers produced in accordance with the above-described methods are also provided. One preferred one-piece lidded container structure includes a bottom tray formed from a first length of thermoplastic material, and a top corresponding lid formed from a second length of thermoplastic material. A secured juncture is formed from the lengths of thermoplastic material thereby allowing alignment of the bottom tray and top lid in an axially opposing orientation upon closure.
Advantageously, the present invention provides unique methods of making one-piece lidded containers and containers made by the same that allow dissimilar materials to be economically used. These and other advantages of the invention will readily apparent from the description set forth below.